Improve p2p error handling to propagate errors
from the origin up the call chain the Server peer removal code
using a new PeerError type containing a DiscReason and a more detailed
description.
The origin can be tracked down using PeerErrorCode (code) and DiscReason
(reason)
which looks like this in the log:
> [TRACE] [08-28|16:33:40.205] Removing p2p peer peercount=0
url=enode://d399f4b...@1.2.3.4:30303 duration=6.901ms
err="PeerError(code=remote disconnect reason, reason=too many peers,
err=<nil>, message=Peer.run got a remote DiscReason)"
The most visible change is event-based dialing, which should be an
improvement over the timer-based system that we have at the moment.
The dialer gets a chance to compute new tasks whenever peers change or
dials complete. This is better than checking peers on a timer because
dials happen faster. The dialer can now make more precise decisions
about whom to dial based on the peer set and we can test those
decisions without actually opening any sockets.
Peer management is easier to test because the tests can inject
connections at checkpoints (after enc handshake, after protocol
handshake).
Most of the handshake stuff is now part of the RLPx code. It could be
exported or move to its own package because it is no longer entangled
with Server logic.
There were multiple synchronization issues in the disconnect handling,
all caused by the odd special-casing of Peer.readLoop errors. Remove the
special handling of read errors and make readLoop part of the Peer
WaitGroup.
Thanks to @Gustav-Simonsson for pointing at arrows in a diagram
and playing rubber-duck.
Overview of changes:
- ClientIdentity has been removed, use discover.NodeID
- Server now requires a private key to be set (instead of public key)
- Server performs the encryption handshake before launching Peer
- Dial logic takes peers from discover table
- Encryption handshake code has been cleaned up a bit
- baseProtocol is gone because we don't exchange peers anymore
- Some parts of baseProtocol have moved into Peer instead
